Method of decoratively coloring articles in gold colors and the product thereof



Patented Mar. 9, 19 43 METHOD OF DECORATIVELY COLORING ARTICLES IN GOLD COLORS AND THE PRODUCT THEREOF Jesse E. Stareck, Waterbury, Conn.

No Drawing. Application June 5, 1939, Serial No. 277,445

6 Claims.

This invention relates to a method of decoratively coloring articles in gold colors, and the product thereof, and provides improvements therein.

Decorated articles having colors designed to match that of the metal gold and its alloys are much used in industry and trade. These gold colors are obtained by thin coatings of the metal gold applied chemically or electrolytically. Paints and lacquers are also used which are pigmented with powdered metals, usually alloys of copper.

For industrial or commercial use gold is usually alloyed with copper or silver, or with both, and sometimes with other metals as tin, platinum and others. The percentage of gold in an alloy is designated by its number of parts in twentyfour, pure gold being rated 24 carat. The colors of these alloys are likewise designated by carat number. Accordingly there are -a number of colors called gold corresponding to the carat number of the gold alloy and also to the shade resulting from the use of difierent metals for alloying with gold. The plates of gold and its alloys are relatively expensive and they are of uneven thickness, which in thin plates give uneven colors. Bronze powders are made which fairly well imitate colors of difierent carat gold, but from the standpoint of wear, adherence, and close matching of color, paints and lacquers pigmented with bronze powders have limitations. It is also well known that color-matching where pigments are used, is a diflicult art. Lacquers also run in the process of applying them, resulting in unevenness of color.

has a thin translucent coating of copper, and,

By the present invention I provide a method by which decorative coatings may be applied to metals which are adherent, by which the colors of gold of various carat number and difierent alloys thereof may be closely matched, which is susceptible to a close control so as to give reproducible results and thereby avoid many of the diiliculties of matching colors, and which is susceptible to the production of most if not all gold colors by simple variations in the mode of procedure in the practice of the method. The invention further provides a method which gives an even color, and which is less expensive than gold plating.

The invention further provides a novel product or article having a decorated gold color.

According to the present invention I take an article of the group: silver, light colored silver alloys, nickel, light colored nickel alloys, brass, and light colored copper alloys, or, articles coated when viewed, has a color which is a blend of the color of the reduced copper layer and or the metal or alloy beneath it.

By varying the thickness of the cuprous oxide layer, and thereby the thickness of the copper layer resulting from the reduction of the cuprous oxide, suit-able combinations can be obtained to match golds of various carat, and of various alloys.

To obtain a very close match to the color of a given gold alloy a thin coating of cuprous oxide may be electrodeposited on the reduced copper, and the shade of this cuprous oxide layer blending with the colors of the copper layer and of the metal or alloy beneath gives a decorative gold shade which closely matches a desired gold color or shade.

A clear lacquer is advantageously applied over the copper or cuprous oxide to protect it from wear and from the effects of the atmosphere.

The desired thin'transparent copper layers are obtained by electrodepositing cuprous oxide layers having a thickness approximately from- 0.3 millionth to 1 millionth of an inch. The cuprous oxide deposits may be obtained by the method disclosed in my Patent 2,081,121.

An examplefollows of a procedure for obtaini 'ing the desired thickness of cuprous oxide for reduction to copper, by which the thickness may be controlled and determined by the time or duration of electrodeposition. A bath having the following make-up composition is prepared.

The deposition rate is so adjusted as to give the second order of green in five minutes. This may be done by adjustment of the sodium hydroxide and by adjustment of the temperature. A temperature around 70 F., and an equilibrium current density of about A ampere per square foot is advantageous with the bath made up and adjusted as described. The above-mentioned thicknesses of cuprous oxide for obtaining the copper layer by reduction, may be obtained by thereon is then placed in an alkaline solution,

connected as cathode, current passed, and the cuprous oxide electrolytically reduced to copper. A solution of sodium carbonate may be used as well as solutions of other alkali compounds such as are commonly used for electrolytic cleaning.

When the reduction of-cuprous oxide is done in a cold alkaline bath (ordinary room temperature), the reduced copper has a brown shade, which I attribute to the presence of hydrogen, either as absorbed hydrogen or as a copper hydride.

To remove any brown shade which the copper reduced from the cuprous oxide may have, I dip the article in a weak acid solution, allowing the article to remain therein for a few seconds; for example, about five seconds. For the acid dip, I have used'a water solution of about 1 to sulphuric acid. After dipping in the weak acid solution the article is rinsed in water.

There is an advantage in using a cold alkaline solution for reduction, inasmuch as the reduced copper, when the reduction of cuprous oxide is done in a hot alkaline bath, is quite susceptible to tarnishing. On the other hand, the occluded hydrogen or copper hydrides, and consequently the brown shade of the reduced copper, may be minimized or even avoided by reducing at a low voltage in a hot alkaline bath in which case the dipping of the copper reduced from the cuprous oxide, in the weak acid solution, may be omitted. When the acid dip is used with the thicker layers, I deposit the cuprous oxide and dip in two or more steps.

The thickness of the copper layer reduced from the cuprous oxide will have a thickness somewhat less than that of cuprous oxide, which I estimate by calculations from the densities of the two materials to be about two-thirds.

The darker shades of gold or gold alloys are sodium carbonate solution. The article with its reduced copper layer was then dipped in a 1% solution of sulphuric acid for about 5 seconds, and then rinsed in water. The article was then placed in the aforementioned bath and cuprous oxide electrodeposited for 8 seconds. After rinsing in water and drying, a coat of clear lacquer was applied thereto.

To protect the decorated article from wear, and also from weather conditions a coat of a clear lacquer may be applied thereto, after the cuprous oxide layer has been reduced as aforesaid, or after the cuprous'oxide layer has been deposited on the copper reduced from the previously applied cuprous oxide electrodeposit.

The decorative electrodeposits obtained by the present method have excellent adherence. Moreover the results in matching gold colors are exceptional, in that the color is even or uniform over the entire article, even on articles having deeply recessed and protruding portions. A corresponding evenness or uniformity of color could not be obtained by copper plating directly, or even by plating with gold or gold alloys in thin layers or films.

The method, with a properly adjusted bath, and with a controlled temperature and voltage, is an instrument of precision, and by its use a desired result can be very exactly reproduced, and, by appropriate determinations of the thickness of the layer of copper reduced from the cuprous oxide, and also, where used, of the thickin general obtained by electrodepositing the thicker cuprous oxide electrodeposits and reducing them, and the lighter golds or gold alloys by putting on the thinner cuprous oxide electrodeposits and reducing these.

Many shades of gold or gold alloys may be obtained by the blend which is obtained from the copper layer and the metal surface below it.

Other shades of gold, or gold alloys, may be obtained by electrodepositing on the copper re,- duced from the cuprous oxide, a thin coating or layer of cuprous oxide. The cuprous oxide is deposited to a thickness of about of a millionth of an inch or less, depending on the shade of gold which it is desired to match. This range ness of the cuprous oxide layer, desired shades of gold, or gold alloys may be matched with great exactness.

Dark colored metals and alloys may be given a gold color, according to the-present method, by first electrode positing thereon a coating of brass or of light colored alloys, or of nickel, or of silver, or a light colored alloy of nickel or silver.

The invention may be practiced by other modes of procedure than that herein specifically described.

What is claimed is:

1. An article having a decorative gold color comprising a layer of a metal or alloy of the group silver, light colored silver alloys, nickel, light colored nickel alloys, brass, light colored copper alloys, and a thin even layer of copper thereon which is reduced from electrodeposited cuprous oxide through which the color of the underlying layer is apparent as a blend thereof with the color of the outer layer, the thickness of said reduced copper not exceeding approximately one millionth of an inch.

2. An article having a decorative gold color according to claim 1, further including a thin layer of cuprous oxide not exceeding about threetenths of a millionth of an inch.

3. A method of decoratively gold coloring articles, comprising electrodepositing a layer of cuprous oxide approximately three-tenths to one millionth of an inch thick on an article having a surface portion of a metal or alloy of the group silver, light colored silver alloys, nickel, light colored nickel alloys, copper alloys, and reducing the cuprous oxide to copper, said copper obtained by the reduction of the cuprous oxide being characterized by its evenness of thickness resulting from the evenness with which cuprous oxide is electrodeposited.

4. A method of decoratively gold coloring articles, comprising electrodepositing a layer of cuprous oxide approximately three-tenths to one millionth of an inch thick on an article having a surface portion of a metal or alloy of the group silver, light colored silver alloys, nickel, light colored nickel alloys, copper alloys, reducing the cuprous oxide to copper in a cold alkaline solution and dipping in a weak acid solution, said copper obtained by the reduction of the cuprous oxide being characterized by its evenness of thickness resulting from the evenness with which cuprous oxide is electrodeposited.

5. A method of decoratively gold coloring articles, comprising electrodepositing a layer of cuprous oxide approximately three-tenths of to one millionth of an inch thick on an article having a surface portion of a metal or alloy of the group silver, light colored silver alloys, nickel, light colored nickel alloys, copper alloys reducing the cuprous oxide to copper and electrodepositing cuprous oxide not exceeding about three-tenths of a. millionth of an inch thick said copper obtained by the reduction of the cuprous oxide being characterized by its evenness of thickness resulting from the evenness with which cuprous oxide is electrodeposited.

6. A method of decoratively gold coloring articles, comprising electrodepositing a layer of cuprous oxide approximately three-tenths to one millionth of an inch thick on an article having a surface portion of a metal or alloy of the group silver, light colored silver alloys, nickel, light colored nickel alloys, brass, light colored copper alloys, reducing the cuprous oxide to copper in a cold alkaline solution, dipping in a weak acid solution and electrodepositing cuprous oxide not exceeding about three-tenths of a millionth of an inch thick said copper obtained by the reduction of the cuprous oxide being characterized by its evenness of thickness resulting from the evenness with which cuprous oxide is electrodeposited.

JESSE E. STARECK. 

